Method of cleaning air supply systems and ducts



Dec. 23, 1969 STEPHENS I 3,485,671

METHOD OF CLEANING AIR SUPPLY SYSTEMS AND DUCTS Filed Dec. 19, 1966 2 Sheets-Sheet 1 IN VENTOR.

I nrmmsvs Dec. 23, 1969 5. R. STEPHENS METHOD OF CLEANING AIR SUPPLY SYSTEMS AND DUCTS Filed Dec. 19, 1966 2 Sheets-Sheet 2 \f I N VENTOR.

ATTOKNE Y5 United States Patent 3,485,671 METHOD OF CLEANING AIR SUPPLY SYSTEMS AND DUCTS George R. Stephens, Richmond, 'Calif., assignor to Food Products, Inc, Richmond, Calif., a corporation of California Filed Dec. 19, 1966, Ser. No. 602,815 Int. Cl. B08 9/06, /02

US. Cl. 134--7 1 Claim ABSTRACT OF THE DISCLOSURE The steps of rapidly withdrawing the air from a downstream station of air supply systems and air supply ducts while introducing into an upstream station thereof under a supra-atmospheric pressure a relatively finely divided material having a low specific gravity and a lesser hardness than the materials forming such supply systems and ducts.

SUMMARY OF THE INVENTION The removal from air supply systems and air supply ducts of wall deposits of dirt and dust without damage to such systems and ducts characterized by the high velocity flushing of the same with a finely divided light weight metal polishing solid entrained in air.

THE DRAWINGS FIG. 1 is a view in perspective of apparatus suitably adapted for the practice of the subject method;

FIG. 2 is a view in cross-section of an air supply duct in the course of being cleaned by the process of the invention;

FIG. 3 illustrates to scale pieces of felt, a material suitable for use in the process of the invention; and

FIG. 4 is an enlarged detail view of the apparatus of FIG. 1.

Referring to the drawings, a typical air supply system for the heating and air conditioning of buildings comprises an air supply duct having ceiling outlets 12 and 14. As is well known, such ducts become laden over a period of time with wall deposits of dirt, dust, lint and the like, to the point where a clean-out operation is required. This operation is conventionally carried out manually with brushes and vacuuming equipment with considerable labor and expense. The cleaning method of the invention enables the cleaning of such ducts and duct systems quickly, efficiently and economically.

Disposed in sealed off air-receiving relation to outlet 14 is an air and cleaning material handling system comprising conduit 16, separator 18, conduit 20, filter unit 22, conduit 24 and air evacuator unit 26. Disposed within outlet 12 is the output end of a flexible conduit 28 which is adapted to introduce comminuted cleaning material 30 into duct 10, said material being fed from a hopper 32 by a feed blower 34.

Separator 18 comprises a settling out chamber 35 and a collector 36 for the cleaning material 30, the dirt and dust laden air passing therefrom through conduit 20 to the filter unit 22.

Filter unit 22 is of the dust arrester type, containing,

Patented Dec. 23, 1969 for example, a multi-pocketed filter cloth 38, a vibrator bar 40, and a direct collection chamber 42.

Filtered air passes through conduit 24 into chamber 44 and therefrom through discharge outlet 46. Chamber 44 contains one or more fans 48 mounted on shaft 50, the latter being driven by motor 52.

The described apparatus withdraws air and the cleaning material entrained therein from duct 10 at a rate on the order of 3200 c.f.m., while blower 34 delivers air with entrained cleaning material at a rate on the order of 5G0700 c.f.m.

A preferred cleaning material is walnut shells, preferably broken up to about the fineness of coarse sand. Other suitable materials, for example, are felt, foam plastic and polystyrene of various particle sizes and shapes, such, for example, as shown in FIG. 3. The materials are sufficiently light in weight to be brought into contact over a relatively brief period of time with the entire internal surf-ace of the duct under the swirling, turbulent flow of air (FIG. 3) caused by the activity of fan 48 and feed blower 34. Also, these materials have a hardness less than that of sheet aluminum and galvanized steel, materials of which air ducts are normally made, and hence they have a skidding, wiping action on the duct walls rather than a bouncing, abrading action, i.e. such action as makes for maximum duct surface contact per particle per passage through the duct. Other necessary characteristics which the above-mentioned materials have are relatively small particle size and multiple points or sharp edges on the pieces or granules. It is only with a material having such properties and characteristics that the four corners of rectangular air ducts may be satisfactorily cleaned.

The specific gravity of comminuted w-alnut shells is just slightly greater than that of water, while the specific gravities of felt, foam plastic and polystyrene are substantially less than that of water.

The specific material to be selected for any given duct cleaning job depends upon the following: the amount of wearing away action required to etfectcleaning; the air speed obtainable with the vacuum equipment used, such speed varying with changes in size of the air ducts; and the shape and contour of the air supply system, including fans, cooling coils and heating coils. For example, with ducts of average cross-sectional area which require a strong wearing away action for cleaning, the walnut shell material would be an appropriate selection. For large size ducts, e.g those of two feet and more in width, an appropriate selection would be a lighter material of the type of felt, foam plastic and polystyrene; felt or polystyrene being preferred where strong cleaning action is required; and foam plastic where a weaker cleaning action is called for.

Among the specific advantages of the subject cleaning method are the following: the anemostats, registers, fans, turn vanes and louvres forming parts of the air supply systems may be cleaned in place; and the air ducts can be cleaned without the necessity of putting a man in the false ceiling area to make access holes in the air ducts for cleaning, thereby avoiding risk of damage to the ceilmg.

What is claimed is:

1. A process for removing wall deposits from an air supply system having air ducts of rectangular cross-sectional area on the order of one square foot comprising evacuating the air from a downstream station of said sys- 2,367,918 1/1945 Bartel 134-37 XR tern at a rate 011 the order of 3200 c.f.m. while blowing 2,426,072 8/1947 Wall et a1.

into an upstream station of said system at a rate on the 2,622,047 12/1952 Ayers 1347 order of 600 c.f.m. air having entrained cleaning material, 2,627,149 2/ 1953 Mac Cracken 134-7 XR said material being selected from the group Consisting of 5 2,948,092 8/1960 Fuller 51-320 XR Walnut shell, felt, foam plastic and polystyrene, said mate- 2,972,502 2/ 1961 Jennings et a1. 153 XR rial being in the form of relatively small particles of gen- 3,033,711 5/ 1962 Harding 134-7 erally irregular shape having relatively sharply defined 3,090,166 5/1963 Straub.

edges and points, said cleaning material skidding over the duct walls in a swirling, turbulent flow caused by the difl 0 MO S O, WOLK, Primary Examiner ferentlal between the air flow input and output rates. JOSEPH T. Z AT AR G A, AsSiStant EXaminer References Cited UNITED STATES PATENTS 2 0 7 94 7 1937 l l5 l5-3.5, 302; 51-320; 1348, 21

US. Cl. X.R. 

